Multi-load refrigeration system with multiple parallel evaporators

ABSTRACT

System and method for reducing temperature variation among heat dissipating components in a multi-component computer system. In this respect, component temperatures are controlled to remain relatively constant (approximately within 5° C.) with respect to other components, while allowing for multiple fluctuating heat loads between components. A refrigeration system possessing a variable speed compressor or a constant speed compressor is utilized to control the flow of refrigerant through the refrigeration system. The temperature variation among components is reduced by independently metering the mass flow rate of the refrigerant flowing into each component to compensate for the amount of heat load on each component. In this respect, the mass flow rate of the refrigerant entering into each of the evaporators is metered by valves located upstream from each of the evaporators. In another respect, the mass flow rate is metered by the above-described valves and a main valve provided on a secondary refrigerant line.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of currently pending U.S. applicationSer. No. 09/801,909 filed on Mar. 9, 2001, entitled “Multi-LoadRefrigeration System with Multiple Parallel Evaporators”, assigned tothe present assignee and incorporated herein by reference, now U.S. Pat.No. 6,415,619.

FIELD OF THE INVENTION

This invention relates generally to a system for reducing thetemperature of components in a computer system. More particularly, theinvention pertains to a refrigeration system having multiple evaporatorsconnected in parallel for receiving individually metered amounts ofrefrigerant to thus reduce temperature variation among components in amulti-component system.

BACKGROUND OF THE INVENTION

The components (e.g., processors, micro-controllers, high speed videocards, disk drives, semi-conductor devices, etc.) of a computer systemare generally known to generate rather significant amounts of heat. Ithas been found that the performance and reliability of the componentstypically deteriorate as the temperature of the components increase.Computer systems are thus generally equipped with a mechanism (e.g., afan) attached to a housing of the computer system to cool the componentsby cooling the interior space of the computer system. Although thesetypes of mechanisms have been relatively effective in cooling thecomponents of certain types of computer systems, they have been found tobe relatively insufficient to cool the faster and more powerfulcomponents of today's computers.

With the advent of faster and more powerful processors, the possibilitythat the processors will overheat has drastically increased. Onesolution to the overheating problem has been to directly cool thecomponents themselves through the use of refrigeration systems.Refrigeration systems generally possess an evaporator positioned inthermal contact with a surface of the component to be cooled. Althoughrefrigeration systems have been found to be relatively effective inmaintaining the temperatures of individual computer components withinacceptable ranges, it has been found that known refrigeration systemssuffer from a variety of drawbacks and disadvantages when a computersystem possesses a number of components (“multi-component system”).

For instance, one known technique of reducing the temperature of amulti-component system is to rely upon a single refrigeration systempossessing a plurality of evaporators aligned in series along each ofthe components. That is, the evaporators are connected along a singlerefrigerant line such that refrigerant flows from one evaporator to thenext. In this respect, the amount of refrigerant flowing into each ofthe evaporators is the same for each of the evaporators. Thus, knownserially positioned evaporators do not allow for individual metering ofrefrigerant flow through each evaporator. As a consequence, evaporatorspositioned downstream from other evaporators may be adversely affected(e.g., downstream evaporators may receive superheated fluid which mayactually cause a rise in their temperature). In addition, evaporatorspositioned relatively upstream and having lower power dissipation, mayactually be cooler than the downstream evaporators.

An additional problem associated with known multi-load refrigerationsystems arises from the fact that the flow rate through each of theevaporators is the same. In this respect, components producing a greateramount of heat will require a greater amount of refrigerant thancomponents producing a relatively lesser amount of heat. This may causethe refrigerant to remain in liquid form as it enters the compressor.One possible effect of having liquid refrigerant enter into thecompressor is that slugging may occur, which may ruin or otherwisedamage the compressor.

Another manner of reducing the temperature of processors may include theprovision of a separate refrigeration system for each component in amulti-component system. Although such a system may overcome some of thedifficulties of serially positioned evaporators, the cost and spacerequirements involved with this type of system would be relativelysubstantial and thus may not be a viable technique for cooling thecomponents.

SUMMARY OF THE INVENTION

According to the principles of the present invention, a refrigerationsystem is configured to allow for the mass flow rate of refrigerantflowing into the evaporators of a multi-load refrigeration system to beindependently metered to thereby separately control the amount of heatdissipated by each of the evaporators, without suffering from thedrawbacks and disadvantages associated with known refrigeration systems.

According to a preferred embodiment, the present invention relates to arefrigeration system for cooling a plurality of components in a computersystem. The refrigeration system includes a compressor for controllingthe flow of refrigerant through a refrigerant line and a plurality ofevaporators configured to receive the refrigerant flowing from thecompressor. The evaporators are configured for thermal attachment to theplurality of components, and the flow of the refrigerant into each ofthe evaporators is independently metered.

Additionally, the present invention pertains to a method for coolingmultiple components of a computer system having multiple fluctuatingheat loads. According to the method, a flow of refrigerant through arefrigeration system having a variable speed compressor is controlled.The refrigeration system includes a plurality of evaporators and aplurality of valves, each valve being configured to control the flow ofthe refrigerant through a respective evaporator. A saturationtemperature of the refrigerant is sensed and the speed of a compressoris modified in response to the saturation temperature being outside apredetermined saturation temperature range.

In accordance with another preferred embodiment, the present inventionrelates to a method for cooling multiple components of a computer systemhaving multiple fluctuating heat loads. According to the method, a flowof refrigerant through a refrigerant line in a refrigeration systemhaving a constant speed compressor is controlled. The refrigerationsystem further includes a plurality of evaporators and a plurality ofvalves, each of the valves is configured to meter the flow of therefrigerant through a respective evaporator. A superheat temperature ofthe refrigerant flowing through each of said evaporators is checked.Each of the respective valves for the evaporators in which theevaporator superheat temperature is less than an evaporator superheattemperature set point is manipulated to decrease the flow of refrigeranttherethrough. A processor temperature is sensed for those evaporators inwhich the evaporator superheat temperature exceeds or is equal to theevaporator superheat temperature set point.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention will become apparent tothose skilled in the art from the following description with referenceto the drawings, in which:

FIG. 1 illustrates a refrigeration system for cooling components of acomputer system in which a plurality of evaporators are positioned in aparallel configuration in accordance with an embodiment of the presentinvention;

FIG. 2 is a flow chart depicting a manner in which the embodimentillustrated in FIG. 1 may be practiced;

FIG. 3 illustrates a refrigeration system for cooling components of acomputer system in accordance with another embodiment of the presentinvention;

FIG. 4 is a flow chart depicting a manner in which the embodimentillustrated in FIG. 3 may be practiced;

FIG. 5 illustrates a refrigeration system for cooling components of acomputer system in accordance with yet another embodiment of the presentinvention; and

FIG. 6 is a flow chart depicting a manner in which the embodimentillustrated in FIG. 5 may be practiced.

DETAILED DESCRIPTION OF THE INVENTION

For simplicity and illustrative purposes, the principles of the presentinvention are described by referring mainly to exemplary embodimentsthereof, particularly with references to a computer system possessingmultiple processors. However, one of ordinary skill in the art wouldreadily recognize that the same principles are equally applicable to,and can be implemented in, a computer system possessing multipleprocessors and other heat producing components and any device that maybenefit from multiple evaporators arranged in parallel, and that anysuch variation would be within such modifications that do not departfrom the true spirit and scope of the present invention. Thus, althoughthe present invention is described with particular reference toprocessors, it will be apparent to one of ordinary skill in the art thatthe present invention may be practiced with any other suitable heatdissipating component.

In accordance with the principles of the present invention, temperaturevariation among processors in a multi-processor system may be reducedthrough the use of a refrigeration system (e.g., a vapor compressionrefrigeration system). In this respect, processor temperatures may becontrolled to remain relatively constant (approximately within 5° C.)with respect to other processors, while allowing for multiplefluctuating heat loads among the processors. That is, according to theprinciples of the present invention, the mass flow rate of refrigerantflowing into each evaporator attached to a processor is independentlymetered to compensate for the amount of heat load for each processorwhile the temperature of refrigerant entering each evaporator issubstantially equal.

In FIGS. 1, 3, and 5, multi-load refrigeration systems 10, 150, 250 areillustrated as including a plurality of evaporators 12, 14, 16, 18(e.g., cold plates) which are connected in a parallel fashion to oneanother to cool multiple processors (not shown) in a computer system.Multi-load refrigeration systems, as referenced throughout the presentdisclosure, generally refer to refrigeration systems having a pluralityof evaporators for cooling multiple heat loads generated by multipleprocessors. Because the specific type of evaporator to be used in thepresent invention will vary according to individual needs, the presentinvention is not limited to any specific type of evaporator and may thusutilize any type of evaporator which may reasonably accomplish the goalsof the present invention. Examples of suitable evaporators employable inthe present invention are available from LYTRON, Inc. of Woburn, Mass.and THERMOTEK Co., LTD. of Texas and South Korea. However, as is readilyapparent to those of ordinary skill in the art, other suitableevaporators may be used in the present invention without departing fromthe scope and spirit of the present invention.

Additionally, although FIGS. 1, 3, and 5, each depict four evaporators,it is to be understood that the present invention is not limited to fourevaporators, but rather, the present invention may include anyreasonable number of evaporators. In one respect, the number ofevaporators may correspond to the number heat dissipating processors.Accordingly, the four evaporators depicted in FIGS. 1, 3, and 5 are forillustrative purposes only and thus is not meant to limit the presentinvention in any respect. Additionally, as is well known to those havingordinary skill in the art, the term “parallel” describes the manner inwhich a single conduit is separated into a plurality of conduits, suchthat, the flow of refrigerant through each of the conduits may beindependently controlled.

Referring to FIGS. 1, 3, and 5, the multi-load refrigeration systems 10,150, and 250 each possesses a closed loop for refrigerant to flow to andfrom the processors of the refrigeration systems. The refrigerationsystems 10, 150, 250 each includes a plurality of evaporators 12-18, acompressor 30, a condenser 36, and an expansion valve 42. The condenser36 and the expansion valve 42 of the present invention may include anynumber of known or heretofore known condensers and expansion valves andthus includes any type of condenser and expansion valve whichsubstantially adequately performs their respective functions within arefrigeration system. Examples of expansion valves suitable for use withthe present invention include capillary tubes, constant pressureexpansion valves, and the like.

Additionally, any suitable type of refrigerant may be utilized in thepresent invention. In fact, the choice of refrigerant will depend upon aplurality of factors, e.g., cooling requirements, environmental impact,cost, etc. Generally speaking, suitable refrigerants include the suiteof vapor compression hydrocarbon refrigerants (CFCs, HCFSs, HFCs or anyblend of pure refrigerants). Specific examples of suitable refrigerantsinclude R134a, R290, R600, etc. Moreover, suitable refrigerants may beobtained from any commercial refrigerant manufacturer (e.g., TONG TAIINTERNATIONAL located in Taiwan, R.O.C.).

According to the preferred embodiment illustrated in FIG. 1, thecompressor 30 is a variable speed compressor. In other words, thecompressor 30 may be controlled to either increase or decrease the massflow rate of the refrigerant therethrough. According to the principlesof the present invention, a number of different types of variable speedcompressors may be utilized for proper operation of the presentinvention. Thus, in similar fashion to other types of vapor compressionrefrigeration systems, the refrigerant flowing through the refrigerantline 20 changes between a gas and a liquid at various positions as therefrigerant circuits the closed loop of the refrigeration system 10.

Although not specifically shown in FIG. 1, the evaporators 12-18 areconfigured to be attached to respective processors by any known meanswhich allows for adequate thermal transfer from the processors to theevaporators.

In operation, refrigerant flowing into each of the evaporators 12-18 isindividually metered. In one respect, the mass flow rate of therefrigerant flowing into each of the evaporators 12-18 is generallydependent upon the amount of heat produced by a respective processor.That is, because the level of cooling of the processors depends upon theamount of refrigerant flowing into the evaporators 12-18, the mass flowrate of the refrigerant is metered to allow a controlled amount ofrefrigerant to enter into the respective evaporators. Additionally,according to a preferred embodiment of the invention, the evaporators12-18 only receive a relatively necessary amount of refrigerant toadequately cool each respective processor without allowing anysignificant amount of liquid refrigerant to flow into the compressor 30.In this respect, evaporators attached to processors producing relativelyless heat than other processors may receive relatively less refrigerant.Thus, the temperatures of the processors in a multi-processor system maybe maintained at a relatively constant temperature to thereby reduce anytemperature variation among the processors.

Referring again to FIG. 1, refrigerant enters the variable speedcompressor 30 through a compressor inlet 32. The variable speedcompressor 30 increases the pressure and temperature of the refrigerantbefore the refrigerant exits through a compressor outlet 34. The speedof the compressor 30 and thus the level of compression of therefrigerant may be controlled by a proportional, integral, derivativecontroller with relay (“PID”) 60. The manner in which the compressionlevel is controlled by altering compressor speed will be discussed ingreater detail hereinbelow.

The refrigerant thus flows out of the compressor 30 and through therefrigerant line 20 into the condenser 36 through a condenser inlet 38.Within the condenser 36, the refrigerant begins to decrease intemperature while remaining at a constant pressure until the refrigerantreaches a saturation point. The refrigerant exits the condenser 36through a condenser outlet 40, typically as a liquid (still at arelatively high pressure and temperature). The refrigerant then flowsthrough the refrigerant line 20 into the expansion valve 42 through anexpansion valve inlet 44. The pressure of the refrigerant is reducedwithin the expansion valve 42.

After exiting the expansion valve 42 through an expansion valve outlet44, the refrigerant flows past a sensor 66 which measures the evaporatorsaturation temperature (“T_(sat)”) of the refrigerant. Although anysuitable type of temperature sensor may be utilized in the presentinvention, examples of suitable temperature sensors include athermocouple, thermistor, pressure sensing device if the refrigerant isazeotropic (i.e., evaporator saturation temperature is constant overphase change), and the like. The sensor 66 is connected to the PID 60via an input line 62. The PID 60 is also connected to the variable speedcompressor 30 via an output line 64. The PID 60 is configured to controlthe speed of the compressor and thus the level of compression thevariable speed compressor 30 applies on the refrigerant based upon themeasured T_(sat) to thereby control the mass flow rate of therefrigerant throughout the refrigeration system 10. Although anysuitable PID may be utilized with the present invention, examples ofsuitable PIDs include those manufactured by OMEGA Inc. of Stamford,Conn., and WATLOW ELECTRIC MANUFACTURING CO. of St. Louis, Mo. Therefrigerant then flows through the refrigerant line 20 and is separatedinto four evaporator refrigerant lines 22-28 at a junction 46. Theevaporator refrigerant lines 22-28 lead the refrigerant through theevaporators 12-18.

As illustrated in FIG. 1, evaporator valves 52-58 are provided upstreamof respective evaporators 12-18 to individually meter the flow ofrefrigerant into each of the evaporators. It is to be understood that aspecific type of evaporator valve is not required to be utilized withthe present invention, but rather, any suitable type of controllablemetering valve, e.g., a thermal electric valve, may be utilized. Anexample of a suitable evaporator valve employable in the presentinvention includes the 625 Series Valves manufactured by PARKER-HANNIFINCORP. of Cleveland, Ohio.

As further illustrated in FIG. 1, sensors 82-88 (e.g., thermocouples,thermistors, pressure sensing devices, etc.) are positioned downstreamof respective evaporators 12-18. The sensors 82-88 are configured tomeasure the temperature of the refrigerant (“T_(evap,out)”) as it exitsthe respective evaporators 12-18. The evaporator valves 52-58 respond tochanges in the T_(evap,out) to meter the flow of the refrigerant intoeach of the evaporators 12-18. In one respect, a change in theT_(evap,out) may cause a bimetallic strip inside the evaporator valve52-58 to actuate thus manipulating the evaporator valve to vary the flowof refrigerant into the respective evaporators 12-18. The change intemperature may be relayed to the evaporator valves 52-58 via respectivetemperature signal lines 92-98. After the refrigerant exits theevaporators 12-18, the refrigerant is once again introduced back intothe refrigerant line 20 such that the entire refrigeration process maybe repeated. In addition, a sensor 70 (e.g., thermocouple, thermistor,pressure sensing device, etc.) is provided between the evaporators 12-18and the variable speed compressor 30 so that the suction temperature(“T_(suction)”) may be measured.

FIG. 2 is a flow diagram 100 depicting a manner in which the embodimentillustrated in FIG. 1 may be practiced. Accordingly, the followingdescription of FIG. 2 will be made with particular reference to thosefeatures illustrated in FIG. 1. As seen in FIG. 2, after therefrigeration system 10 is turned on at step 102, the evaporator valves52-58 are opened at step 104. As the refrigerant begins to flow throughthe refrigeration system 10, the T_(sat) is measured at step 106. TheT_(sat) measurement is then relayed to the PID 60 via the input line 62where it is then compared to a predetermined range at step 108. Thepredetermined range in step 108 is determined based upon system designand the amount of load variability to be expected among the processors.In general, the predetermined range may depend upon the following:electrical timing requirements, allowable mechanical stress due tothermal expansion, proximity to dew point, etc. If it is determined thatthe T_(sat) is not within the predetermined range, it is then determinedwhether the T_(sat) is higher than an evaporator saturation temperatureset point (“T_(sat,set)”) at step 110. The T_(sat,set) may be determinedby determining the optimum operating temperature of each processor andis a function of processor design, processor packaging, the efficiencyof the thermal connection between the evaporator and processor, thedesign of the evaporator, flow rate of the refrigerant, refrigerantproperties, and the like.

If the T_(sat) is equal to or below the T_(sat,set), the speed of thevariable speed compressor 30 is reduced by a controlled amount at step112. By reducing the speed of the variable speed compressor 30, the massflow rate of the refrigerant entering into the evaporators 12-18 will bedecreased and the T_(sat) will be increased. If, on the other hand, theT_(sat) is higher than the T_(sat,set), the speed of the variable speedcompressor 30 is increased by a controlled amount at step 114.Increasing the speed of the variable speed compressor 30 has the effectof increasing the mass flow rate of the refrigerant entering into theevaporators while reducing the T_(sat). After each of steps 112 and 114,the T_(sat) is measured once again and the process is repeated.

If the T_(sat) is determined to be within the desired range, theevaporator superheat temperature (“ΔT_(sup)”) for each of theevaporators 12-18 is sensed by the respective sensors 82-88 at step 116.At step 118, it is determined whether the ΔT_(sup) for each of theevaporators 12-18 is within a predetermined desired range. If theΔT_(sup) for one of the evaporators (e.g., evaporator 12) is within thedesired range, then no change is made to the evaporator valve (e.g.,valve 52) of that evaporator. However, if the ΔT_(sup) is not within thedesired range for any of the evaporators 12-18, the ΔT_(sup) for thatevaporator is compared to an evaporator superheat set point(“ΔT_(sup,set)”) at step 120. The ΔT_(sup,set) for each of theevaporators 12-18 is about between 0-5° C. and may be set to beapproximately the same for each of the evaporators.

Thus, for example, if the ΔT_(sup) for one evaporator (e.g., evaporator12) is lower than the ΔT_(sup,set) for that evaporator (e.g., evaporator12), the evaporator valve for that evaporator (e.g., valve 52) ismanipulated by a controlled amount to decrease the mass flow rate of therefrigerant flowing into the evaporator (e.g., evaporator 12) at step122. In addition, by manipulating the evaporator valve (e.g., valve 52)to reduce the mass flow of the refrigerant through the evaporator (e.g.,12), the T_(sup) may be increased and the T_(sat) may be reduced.

If, on the other hand, the ΔT_(sup) for one evaporator (e.g., evaporator12) is not less than the ΔT_(sup,set) for that evaporator (e.g.,evaporator 12), the evaporator valve (e.g., 52) for that evaporator ismanipulated to increase the mass flow of the refrigerant therethrough bya controlled amount as indicated at step 124. By way of increasing themass flow rate of the refrigerant through that evaporator (e.g.,evaporator 12), the T_(sup) may decrease and the T_(sat) may increase.After the evaporator valves 52-58 have been manipulated to eitherincrease or decrease the flow of refrigerant therethrough, the processbeginning with step 106 is repeated.

It is to be understood that the above-description of a preferredembodiment of the present invention made specific reference toevaporator 12 for illustrative purposes only and that the manner inwhich evaporator 12 may be manipulated is equally applicable to theother evaporators 14-18. Additionally, it is to be understood that byway of the principles of the present invention, each of the evaporators12-18 may be independently metered. More specifically, any one or all ofthe evaporator valves 52-58 may be manipulated to decrease the flow ofrefrigerant therethrough while another one of the evaporator valves ismanipulated to increase the flow of refrigerant therethrough.

Thus, although specific reference is made to the manner of controllingone evaporator 12 and one evaporator valve 52, it is to be understoodthat steps 116-124 are carried out for each of the evaporators 12-18,independently of one another and may be done so simultaneously.

FIG. 3 illustrates a second preferred embodiment incorporating theprinciples of the present invention. The refrigeration system 150 of thesecond embodiment is similar to the refrigeration system 10 describedhereinabove and thus only those features which are reasonably necessaryfor a complete understanding of the second embodiment is describedhereinbelow. Two differences from the refrigeration system 10 are thatrefrigeration system 150 includes a constant speed compressor 130 and aprogrammable logic controller (“PLC”) 160. The refrigeration system 150,according the principles of the second preferred embodiment, alsoincludes a plurality of third temperature signal lines 162-168 connectedto respective sensors 82-88 for relaying evaporator superheattemperature readings from the sensors to the PLC 160. Moreover, aplurality of control signal lines 172-178 are connected from the PLC 160to the respective evaporator valves 52-58.

In addition, FIG. 3 depicts the processors 142-148 to be cooled andshows that each of the processors 142-148 are in communication with thePLC 160 via a first set of temperature signal lines 152-158. In thisrespect, according to the principles of the embodiment illustrated inFIG. 3, the temperatures of the processors 142-148 may be directlyrelayed to the PLC 160. However, it is within the purview of the presentdisclosure that the temperature of the processors 142-148 may bemeasured by any reasonable means including the adjusted temperaturemeasurement of a cold plate. Such a modification to the position oftemperature measurement may be accomplished without deviating from thescope and spirit of the present invention.

FIG. 4 is a flow diagram 200 depicting a manner in which the embodimentillustrated in FIG. 3 may be practiced. Accordingly, the followingdescription of FIG. 4 will be made with particular reference to thefeatures illustrated in FIG. 3. As seen in FIG. 4, after therefrigeration system 150 is turned on at step 102, the evaporator valves52-58 are opened at step 204. As the refrigerant begins to flow throughthe system 150, the ΔT_(sup) for each of the evaporators 12-18 is sensedby respective sensors 82-88 at step 206. At step 208, the ΔT_(sup) foreach of the evaporators 12-18 is compared to a ΔT_(sup,set). TheΔT_(sup,set) for each of the evaporators 12-18 is about between 0-5° C.and may be set to vary among the evaporators.

For illustrative purposes only, the following example is made withparticular reference to one evaporator 12 and its related components. Itis to be understood that each of the following steps are equallyapplicable to the other evaporators 14-18 and their relative components,and the steps may be carried out on the other evaporators 14-18concurrently with the steps described hereinbelow with respect to theevaporator 12.

Thus, for example, if the ΔT_(sup) for the evaporator 12 is lower thanthe ΔT_(sup,set) for that evaporator, evaporator valve 52 is manipulatedto decrease the mass flow rate of refrigerant therethrough by acontrolled amount at step 210. By decreasing the mass flow rate ofrefrigerant through the evaporator valve 52, the T_(sat) may be reduced,while the ΔT_(sup) and the processor temperature or adjusted cold platetemperature (“T_(proc)”) may be increased. After the mass flow rate ofthe refrigerant through the evaporator valve 52 has been reduced, theΔT_(sup) for each of the evaporators is checked again at step 206.

If, on the other hand, the ΔT_(sup) for the evaporator 12 is not lessthan the ΔT_(sup,set) for that evaporator, the T_(proc) is sensed (e.g.,with a thermocouple) at 212. The temperature of the processor 142 isrelayed to the PLC 160 via temperature signal lines 152 and 170. It isthen determined whether the T_(proc) is within a predetermined range atstep 214. The predetermined range in step 214 is determined based uponsystem design and the amount of load variability expected among theprocessors. In general, the predetermined range may depend upon thefollowing: electrical timing requirements, allowable mechanical stressdue to thermal expansion, proximity to dew point, etc. If the T_(proc)is within the predetermined range, the amount of refrigerant flowingthrough the evaporator valve 52 is unchanged and the superheattemperature is checked again at step 206.

If the T_(proc) is outside the predetermined range, the T_(proc) iscompared to a set point temperature to determine whether the T_(proc) istoo hot at step 216. The set point temperature is a preferable operatingtemperature of the component and is generally provided by the componentmanufacturer. The preferable operating temperature is normallydetermined based upon the wafer manufacturing process, yield, frequency,etc. If the T_(proc) is too hot, then the PLC 160 sends a signal viacontrol signal line 172 to the evaporator valve 52 instructing the valveincrease the mass flow rate of refrigerant therethrough by a controlledamount at step 218. By increasing the mass flow rate of the refrigerantflowing into the evaporator 12, the T_(sat) may be increased, while theT_(proc) and the ΔT_(sup) may be decreased.

If the T_(proc) is not too hot, the PLC 160 sends a signal via controlsignal line 172 to evaporator valve 52 instructing the valve to decreasethe mass flow rate of refrigerant therethrough by a controlled amount atstep 220. By decreasing the mass flow rate of the refrigerant flowinginto the evaporator 12, the T_(sat) may be decreased, while the T_(proc)and the ΔT_(sup) may be increased. After these measures have been taken,the ΔT_(sup) is checked again at step 206.

According to the principles of the second preferred embodiment, theamount of refrigerant flowing into each of the evaporators 12-18 may beindependently metered by the evaporator valves 52-58. Thus, thetemperature of the processors 142-148 may be controlled according to thesuperheat temperature of the refrigerant flowing out of the evaporators.

FIG. 5 illustrates a third preferred embodiment incorporating theprinciples of the present invention. The refrigeration system 250 of thethird embodiment is similar to the refrigeration system 150 and thusonly those features which are reasonably necessary for a completeunderstanding of the third embodiment is described hereinbelow. Onedifference from refrigeration system 150 is that refrigeration system250 may include either a PLC or a solid state temperature controller260. However, for purposes of simplicity, the PLC or solid temperaturecontroller 260 will be referred to herein as a PLC. As also seen in FIG.5, the refrigerant line 20 is split such that an auxiliary refrigerantline 230 may divert at least a portion of the refrigerant directly tothe evaporators 12-18 without allowing the diverted portion of therefrigerant to flow through the condenser 36. Because the divertedportion of the refrigerant does not flow through the either thecondenser 36 nor the evaporator valve 42, the refrigerant in theauxiliary refrigerant line 230 has a considerably higher temperaturethan the refrigerant flowing from the evaporator valve 42 to theevaporators 12-18.

A main valve 240 is provided along the auxiliary refrigerant line 230 tocontrol the amount of diverted refrigerant flowing into the evaporators12-18. The main valve 240 may include a controllable metering valvesimilar to the evaporator valves 52-58. Additionally, the main valve 240is controlled by the PLC 260 via a main temperature signal control line270. The auxiliary refrigerant line 230 is also divided into a pluralityof evaporator lines 232-238 which allows for the diverted refrigerant toenter directly into each of the evaporators without flowing through theevaporator valves 52-58.

In addition, in a similar fashion to the second preferred embodiment,FIG. 5 depicts the processors 142-148 to be cooled and shows that eachof the processors 142-148 is in communication with the PLC 260 via afirst set of temperature signal lines 152-158 which are connected to thePLC via a second temperature line 170. In this respect, according to theprinciples of the embodiment illustrated in FIG. 5, the temperatures ofthe processors 142-148 may be directly relayed to the PLC 260. However,it is within the purview of the present invention that the temperatureof the processors 142-148 may be measured by any reasonable meansincluding the adjusted temperature measurement of a cold plate. Such amodification to the position temperature measurements are taken may beaccomplished without deviating from the scope and spirit of the presentinvention.

FIG. 6 is a flow diagram 300 depicting a manner in which the embodimentillustrated in FIG. 5 may be practiced. Accordingly, the followingdescription of FIG. 6 will be made with particular reference to thefeatures illustrated in FIG. 5. As seen in FIG. 5, after therefrigeration system 250 is turned on at 302, the evaporator valves52-58 are opened at 304. As the refrigerant begins to flow through therefrigeration system 250, the ΔT_(sup) for each of the evaporators 12-18is sensed by respective sensors 82-88 at step 306. At step 308, theΔT_(sup) for each of the evaporators 12-18 is compared to aΔT_(sup,set). The ΔT_(sup,set) for each of the evaporators 12-18 isabout between 0-5° C. and may be set to be approximately the same foreach of the evaporators.

For illustrative purposes only, example is made to one evaporator 12 andits related components. It is to be understood that each of thefollowing steps are equally applicable to the other evaporators 14-18and their related components, and that each of the following steps maybe carried out simultaneously amongst all of the evaporators 12-18.

Thus, for example, if the ΔT_(sup)for the evaporator 12 is lower thanthe ΔT_(sup,set) for that evaporator, evaporator valve 52 is manipulatedto decrease the mass flow rate of refrigerant therethrough by acontrolled amount at step 310. The ΔT_(sup,set) may be determined in themanner discussed hereinabove with respect to the second embodiment. Bydecreasing the mass flow rate of the refrigerant through the evaporator12, the T_(sat) may be reduced, and the ΔT_(sup) may be increased, thuscausing the T_(proc) to be increased.

If, on the other hand, the ΔT_(sup) for the evaporator 12 is equal to orhigher than the ΔT_(sup,set) for that evaporator, the T_(proc) is sensed(e.g., with a diode, temperature resistor placed in the silicon, etc.)at 312. The temperature of the processor 142 is relayed to the PLC 260via temperature signal lines 152 and 170. It is then determined whetherthe T_(proc) is within a predetermined processor temperature range atstep 314. The predetermined temperature processor range is determinedbased upon system design and the amount of load variability expectedamong the processors. In general, the predetermined range may dependupon the following: electrical timing requirements, allowable mechanicalstress due to thermal expansion, proximity to dew point, etc. If theT_(proc) is within the predetermined range, the mass flow rate ofrefrigerant flowing through the evaporator valve 52 is unchanged and thesuperheat is checked again at step 306.

If, on the other hand, the T_(proc) is not within the predeterminedprocessor temperature range, the T_(proc) is compared to a set pointprocessor temperature to determine whether the T_(proc) is too hot atstep 316. The set point processor temperature is a preferable operatingtemperature of the component and is generally provided by the componentmanufacturer. The preferable operating temperature is normallydetermined based upon the wafer manufacturing process, yield, frequency,etc. If the T_(proc) is not too hot, then the main valve 240 ismanipulated to increase the mass flow rate of refrigerant (which has notundergone a reduction in temperature or a change in phase) therethroughby a controlled amount at step 318. By increasing the mass flow rate ofthe refrigerant (which has not undergone a reduction in temperature or achange in phase) flowing into the evaporator 12, the evaporator inlettemperature of the refrigerant is increased, such that the T_(proc) andthe ΔT_(sup) may also be increased. If the T_(proc) is too hot, the mainvalve 240 is manipulated to decrease the mass flow rate of therefrigerant (which has not undergone a reduction in temperature or achange in phase) by a controlled amount at step 320. By reducing thismass flow rate in this manner, the temperature of the refrigerantentering the evaporator 12 may be reduced, such that the T_(proc) andthe ΔT_(sup) may also be decreased.

According to the principles of the third embodiment of the presentinvention, the amount of refrigerant flowing into each of theevaporators 12-18 may be independently metered by the evaporator valves52-58. Additionally, refrigerant which has not undergone reduction intemperature in the expansion valve 42 may be inserted directly into theevaporators 12-18 to thus heat the evaporators. Inserting refrigerantwhich has not undergone a reduction in temperature or a change in phaseinto the evaporators 12-18 may be necessary in the event that at leastone of the processors 142-148 is not producing sufficient heat to causesufficient superheat of the refrigerant. In the event that any of theprocessors 142-148 is not producing sufficient heat, as discussedhereinabove, the main valve 240 is manipulated to increase the mass flowrate of the refrigerant which has not undergone a reduction intemperature or a change in phase to thereby allow the heated refrigerantto enter directly into all of the evaporators 12-18.

However, in order to maintain the temperature of the processors that areproducing sufficient heat, the evaporator valves 52-58 of thoseevaporators 12-18 may be further manipulated to compensate for theincreased temperature of the refrigerant entering into thoseevaporators. Accordingly, the amount of refrigerant (which has notundergone a reduction in temperature) flowing through the auxiliaryrefrigerant line 230 into each of the evaporators need not beindependently metered for each evaporator 12-18.

Although specific reference has been made to processors throughout thepresent disclosure, it is to be understood that the present inventionmay be practiced with any heat dissipating component in a computer.

What has been described and illustrated herein are preferred embodimentsof the invention along with some of their variations. The terms,descriptions and figures used herein are set forth by way ofillustration only and are not meant as limitations. Those skilled in theart will recognize that many variations are possible within the spiritand scope of the invention, which is intended to be defined by thefollowing claims—and their equivalents—in which all terms are meant intheir broadest reasonable sense unless otherwise indicated.

What is claimed is:
 1. A refrigeration system for cooling a plurality ofcomponents in a computer system, said refrigeration system comprising: aconstant speed compressor for controlling the flow of refrigerantthrough a refrigerant line; an expansion valve located generallydownstream of said compressor along said refrigerant line; a pluralityof evaporators, each of said plurality of evaporators being configuredto receive said refrigerant line and configured for thermal attachmentto a respective component; a plurality of valves located between saidexpansion valve and said plurality of evaporators along said refrigerantline; and wherein said flow of said refrigerant into each of saidevaporators is independently metered by a respective one of saidplurality of valves.
 2. The refrigeration system of claim 1, whereinsaid refrigerant line is divided into a plurality of second refrigerantlines upstream of said evaporators and wherein each said secondrefrigerant line is configured to deliver said refrigerant into arespective evaporator.
 3. The refrigeration system of claim 2, furthercomprising an auxiliary refrigerant line configured to supply saidsecond refrigerant lines with pre-cooled refrigerant.
 4. Therefrigeration system of claim 3, wherein said auxiliary refrigerant lineconnects said refrigerant line to said second refrigerant lines toenable said refrigerant to flow into each of the evaporators whilebypassing an expansion valve.
 5. The refrigeration system of claim 4;further comprising: a controller; a plurality of temperature sensorsconfigured to measure the temperatures of the plurality of components ofthe computer system; and a plurality of signal lines, each said signalline connecting an associated temperature sensor to said controller. 6.The refrigeration system of claim 5, further comprising: a main valveprovided on said auxiliary refrigerant line, said main valve beingconfigured to control the flow of refrigerant to the plurality ofevaporators along said auxiliary refrigerant line in response to signalsreceived from said controller.
 7. The refrigeration system of claim 6,further comprising a plurality of second sensors positioned along eachof said plurality of refrigerant lines and generally downstream of eachof said evaporators, each said second sensor being capable of sendingsignals to an associated valve positioned on a respective said secondrefrigerant line to thereby meter the amount of refrigerant enteringinto each said evaporator.
 8. The refrigeration system of claim 1,further comprising: a controller; a plurality of temperature sensorsrespectively provided downstream of each of said evaporators, each saidtemperature sensor being in communication with said controller; aplurality of control signal lines, each said control signal line beingconnected to a respective valve and said controller; and wherein saidcontroller is configured to control each of said valves in response totemperature readings measured by said respective temperature sensors. 9.The refrigeration system of claim 8, further comprising: a plurality oftemperature signal lines configured for connection to respectivecomponents of said computer system and said controller; and wherein saidcontroller is configured to send signals to each of said valves inresponse to temperature readings measured by said respective temperaturesensors and from said respective components.
 10. The refrigerationsystem of claim 8, wherein said controller comprises a programmablelogic controller.
 11. A method for cooling multiple components of acomputer system having multiple fluctuating heat loads, said methodcomprising steps of: controlling a flow of a refrigerant through arefrigerant line in a refrigeration system having a constant speedcompressor and an expansion valve, said refrigeration system furtherincluding a plurality of evaporators and a plurality of valves, each ofsaid plurality of valves being configured to meter the flow of saidrefrigerant through a respective evaporator; and delivering apredetermined amount of refrigerant into each of said evaporators. 12.The method according to claim 11, wherein said step of deliveringcomprises delivering the predetermined amount of refrigerant based upondetected superheat temperatures of the refrigerant exiting eachevaporator.
 13. The method according to claim 11, wherein saiddelivering step comprises: checking a superheat temperature of saidrefrigerant flowing through each of said plurality of evaporators; andmanipulating said valve to decrease the flow of refrigerant through arespective evaporator for each of said plurality of evaporators in whichthe evaporator superheat temperature is less than the evaporatorsuperheat temperature set point.
 14. The method according to claim 13,further comprising: sensing a processor temperature for thoseevaporators in which the evaporator superheat temperature exceeds or isequal to the evaporator superheat temperature set point.
 15. The methodaccording to claim 14, further comprising: determining whether theprocessor temperature for each of those evaporators in which theevaporator superheat temperature exceeds or is equal to the evaporatorsuperheat temperature set point is within a predetermined processortemperature range.
 16. The method according to claim 15, furthercomprising: manipulating said valve to decrease the flow of refrigerantthrough a respective evaporator for each of those evaporators in whichthe processor temperature is below the predetermined processortemperature.
 17. The method according to claim 16, further comprising:manipulating a main valve configured to control the flow of refrigerantthrough an auxiliary line connected to the refrigerant line to increasethe flow of refrigerant through said main valve when at least one ofsaid processors is below the predetermined temperature.
 18. The methodaccording to claim 14, further comprising: determining whether theprocessor temperature is above a predetermined processor temperature forthose evaporators in which the processor temperature is outside thepredetermined processor temperature range.
 19. The method according toclaim 18, further comprising: manipulating said valve to increase theflow of refrigerant through a respective evaporator for each of thoseevaporators in which the processor temperature exceeds the predeterminedprocessor temperature.
 20. The method according to claim 19, furthercomprising: manipulating a main valve configured to control the flow ofrefrigerant through an auxiliary line connected to the refrigerant lineto decrease the flow of refrigerant through said main valve when atleast one of said processors exceeds the predetermined processortemperature.
 21. A system for cooling a plurality of components in anelectronic system, said system comprising: means for controlling theflow of a refrigerant through a refrigerant line; means for varying thepressure of said refrigerant; and means for individually metering theflow of said refrigerant through a plurality of evaporators, each ofsaid evaporators being configured to cool at least one of said pluralityof components.
 22. The system according to claim 21, wherein saidmetering means comprises means for substantially simultaneously meteringthe flow of said refrigerant through each of said evaporators.